The present invention relates to a method and apparatus for generating thermal energy, and more particularly, for the solar cooking of food and water using an offset focus reflecting parabolic dish.
For years proposals have been made for constructing devices to adequately utilize the sun's rays to generate thermal energy, with particular application in the cooking of food or boiling of water, thereby reducing electricity or fuel use necessary for such preparation. The conversation of scarce fuel sources, whether they be petrochemical, wood or dung, is especially acute in developing countries. Forests have been denuded in the search for firewood, wrecking havoc with the delicate balance of local ecosystems. Therefore, any device capable of reducing the need for such scarce, not easily renewable resources, is desireable.
Solar cooking devices have been proposed for such use. U.S. Pat. No. 4,696,285 discloses a solar cooker having an insulated oven affixed to the backside of a primary solar reflector. A secondary reflector reflects the solar radiation from the primary reflector into the oven, which is centered within the primary reflector. The secondary reflector is adjustable so as to vary the amount of solar rays entering the oven. The reflector apparatus is gimballed on a frame which travels about an arcuate path.
U.S. Pat. No. 4,281,644 discloses a solar cooker foldable into a briefcase-type unit. The cooker comprises a pair of housing halves which are pivotally affixed to one another to be moved from a closed to an open position. A pair of support arms carry a spit above the centerpoint of the reflecting dish. U.S. Pat. No. 4,083,357 discloses a parabolic trough reflector having a cooking oven disposed within the trough. Folding leg assemblies are provided, as is a sliding lock member permitting the vertical tracking of the sun. Similarly, U.S. Pat. No. 4,262,660 discloses a solar cooking trough having an expandable parabolic reflector with a solar oven disposed over the centerpoint of the reflector. Extension arms are detachably connected to the solar cooker in order to vary the distance between the reflecting surface and the oven.
Lastly, U.S. Pat. No. 4,274,397 discloses a solar heater having a window cover positioned to transmit solar radiation to a reflector. The reflector reflects the incoming solar radiation to a container. When filled with water, the container may be heated sufficiently to boil the water.